I have a mask which is a sphere, and inside in the sphere another set of models which is the world, and the inner models is slightly popping out of the mask to give the effect of a portal, and the camera is in the background. but how can I make the mask transparent or give that effect, but also have it enclose the model inside it.

Since I can add transparency to the mask but that reveals the object inside. or am I asking for something not possible